Sunlight and the Eye

Background

Sunlight is being shown to have many surprising benefits to the eye, probably via vitamin D. Previous studies have shown that outdoor sunlight exposure during childhood may actually decrease the chances a child will grow up to become nearsighted.

New Study: Sunlight, Vitamin D, and Dry Eye Treatment

A new study published this week in the newsletter of the American Academy of Ophthalmology looked at the role of Vitamin D blood levels in assessing how well artifical tears treat patients with dry eye syndrome. Vitamin D can be synthesized by the body from sunlight or from obtained from nutritional sources such as vitamin D supplements or injections. Given our indoor lifestyle, many people in the United States are Vitamin D deficient. This study showed that while artificial tears improved dry eyes in both patients who had good blood levels of Vitaimn D and in those who had low blood levels of vitamin D, tear quality and tear performance markers were only increased in those patients with good blood levels of Vitamin D. The researchers concluded that their study may show “that vitamin D may act synergistically with topical treatments to harmonize components of the tear film.”

A Note of Caution

Of course, while overall sunlight may have beneficial effects for the eye via blood vitamin D levels, I always remind patients that direct UV light exposure to the eye from sunlight can be harmful. Some researchers feel UV light exposure, for example, over time is linked to cataract formation. Other studies have suggested an association between UV light exposure and the development of macular degeneration. Fortunately, good quality UV-blocking sunglasses that are appropriately labeled do an excellent job of blocking UV light from entering into the eye. And, of course, too much sunlight exposure, particularly during the highest UV times of the day, can lead to skin cancer as well. Sunlight seems to be of most benefit in moderation.